import numpy
import numpy as np
print(np.nan==np.nan)   #false      nan表示空值
print(np.nan!=np.nan)   #true       两个numpy.nan的值不相等

x = np.array([1, 1, 8, np.nan, 10])
print(x)
# [ 1.  1.  8. nan 10.]
y = np.isnan(x)
print(y)
# [False False False  True False]
z = np.count_nonzero(y)
print(z)  # 1

print(np.Inf)     #numpy.inf表示无穷大   Inf = inf = infty = Infinity = PINF

print(np.pi)      #numpy.pi表示圆周率
print(np.e)       #numpy.e表示自然常数e